Just updated /etc/config/nss as posted here
root@OpenWrt:~# cat /etc/config/nss
config nss_firmware 'qca_nss_0'
config nss_firmware 'qca_nss_1'
config nss 'general'
option enable_rps '1'
option enable_log '1'
and nss is working. So, there is no need to include the fstool commit
root@OpenWrt:~# cat /proc/interrupts | grep nss_queue
48: 4113 2513130 0 0 GIC-0 412 Edge nss_queue0
49: 0 0 28283 0 GIC-0 413 Edge nss_queue1
50: 0 0 0 90273 GIC-0 414 Edge nss_queue2
51: 11297 0 0 0 GIC-0 415 Edge nss_queue3
59: 26665 0 563758 0 GIC-0 425 Edge nss_queue0
60: 0 0 0 0 GIC-0 426 Edge nss_queue1
61: 0 0 0 0 GIC-0 427 Edge nss_queue2
62: 0 0 0 0 GIC-0 428 Edge nss_queue3